Trace
Copies an opponent's ability upon entering battle.
Full effect
When this Pokémon enters battle, it copies a random opponent's ability. This ability cannot copy Flower Gift, Forecast, Illusion, Imposter, Multitype, Trace, Wonder Guard, or Zen Mode.
In game description
When it enters a battle, the Pokémon copies an opposing Pokémon's Ability.
Pokemon with Trace
Using Trace in Cobblemon
Abilities are passive and always active, so Trace costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.